Evidence of the complete magnetic reconnection during a sawtooth collapse in a tokamak

Statistical analysis of a large set of current profile data obtained for sawtoothing discharges in the DIII-D tokamak indicates that the safety factor (inverse rotational transform) in the plasma center, [ital q][sub 0], is close to 1.0. The increase of [ital q][sub 0] associated with the sawtooth crash is found to be of the order of 0.05. The results of time resolved measurements of the current profile and the soft x-ray emissions support a model of the sawtooth instability based on total reconnection of the [ital m]=1 magnetic island.